8295156: G1: Improve constant other time calculation

Co-authored-by: Ivan Walulya <iwalulya@openjdk.org>
Reviewed-by: kbarrett, iwalulya

Author: Thomas Schatzl

Diff for: src/hotspot/share/gc/g1/g1GCPhaseTimes.hpp

@@ -390,7 +390,10 @@ class G1GCPhaseTimes : public CHeapObj<mtGC> {
   }
 
   double cur_collection_par_time_ms() {
-    return _cur_collection_initial_evac_time_ms + _cur_optional_evac_time_ms;
+    return _cur_collection_initial_evac_time_ms +
+           _cur_optional_evac_time_ms +
+           _cur_merge_heap_roots_time_ms +
+           _cur_optional_merge_heap_roots_time_ms;
   }
 
   double cur_expand_heap_time_ms() {

Diff for: src/hotspot/share/gc/g1/g1Policy.cpp

@@ -685,7 +685,7 @@ double G1Policy::other_time_ms(double pause_time_ms) const {
 }
 
 double G1Policy::constant_other_time_ms(double pause_time_ms) const {
-  return other_time_ms(pause_time_ms) - phase_times()->total_rebuild_freelist_time_ms();
+  return other_time_ms(pause_time_ms) - (young_other_time_ms() + non_young_other_time_ms());
 }
 
 bool G1Policy::about_to_start_mixed_phase() const {